1: A sled with a plastic dildo on it / the plastic dildo attached to a sled.
2: A penis.

1: Jack: Dude, I added a rod to my sled so i can steer it better.
Jerk: This is amazing, man! We should sell this to kids! We will call it the Zipfy!
Jack: Well the rod I attached to it looks a little like a dick with balls...
Jerk: Who cares? No one'll notice. We can just pay kids 1,000 dollars a piece to prostitute themselves on our sled! We'll be f*cking rich!

2: Bob: I have the biggest zipfy in the world!
Billy: No, I do! I am the one with the biggest zipfy!